Publikationen

Artikel in Referierten Journalen

  • A. Hajizadeh, A. Matysiak, M. Wolfrum, P.J.C. May, R. König, Auditory cortex modelled as a dynamical network of oscillators: Understanding event-related fields and their adaptation, Biological Cybernetics, 116 (2022), pp. 475--499, DOI 10.1007/s00422-022-00936-7 .
    Abstract
    Adaptation, the reduction of neuronal responses by repetitive stimulation, is a ubiquitous feature of auditory cortex (AC). It is not clear what causes adaptation, but short-term synaptic depression (STSD) is a potential candidate for the underlying mechanism. We examined this hypothesis via a computational model based on AC anatomy, which includes serially connected core, belt, and parabelt areas. The model replicates the event-related field (ERF) of the magnetoencephalogram as well as ERF adaptation. The model dynamics are described by excitatory and inhibitory state variables of cell populations, with the excitatory connections modulated by STSD. We analysed the system dynamics by linearizing the firing rates and solving the STSD equation using time-scale separation. This allows for characterization of AC dynamics as a superposition of damped harmonic oscillators, so-called normal modes. We show that repetition suppression of the N1m is due to a mixture of causes, with stimulus repetition modifying both the amplitudes and the frequencies of the normal modes. In this view, adaptation results from a complete reorganization of AC dynamics rather than a reduction of activity in discrete sources. Further, both the network structure and the balance between excitation and inhibition contribute significantly to the rate with which AC recovers from adaptation. This lifetime of adaptation is longer in the belt and parabelt than in the core area, despite the time constants of STSD being spatially constant. Finally, we critically evaluate the use of a single exponential function to describe recovery from adaptation.

  • S. Yanchuk, M. Wolfrum, T. Pereira, D. Turaev, Absolute stability and absolute hyperbolicity in systems with discrete time-delays, Journal of Differential Equations, 318 (2022), pp. 323--343, DOI 10.1016/j.jde.2022.02.026 .
    Abstract
    An equilibrium of a delay differential equation (DDE) is absolutely stable, if it is locally asymptotically stable for all delays. We present criteria for absolute stability of DDEs with discrete timedelays. In the case of a single delay, the absolute stability is shown to be equivalent to asymptotic stability for sufficiently large delays. Similarly, for multiple delays, the absolute stability is equivalent to asymptotic stability for hierarchically large delays. Additionally, we give necessary and sufficient conditions for a linear DDE to be hyperbolic for all delays. The latter conditions are crucial for determining whether a system can have stabilizing or destabilizing bifurcations by varying time delays.

  • S. Amiranashvili, U. Bandelow, Unusual scenarios in four-wave-mixing instability, Physical Review A, 105 (2022), pp. 063519/1--063519/6, DOI 10.1103/PhysRevA.105.063519 .
    Abstract
    A pump carrier wave in a dispersive system may decay by giving birth to blue- and red-shifted satellite waves due to modulation or four-wave mixing instability. We analyse situations where the satellites are so different from the carrier wave, that the red-shifted satellite either changes its propagation direction (k < 0, ω > 0) or even gets a negative frequency (k, ω < 0). Both situations are beyond the envelope approach and require application of Maxwell equations.

  • A.G. Vladimirov, Short- and long-range temporal cavity soliton interaction in delay models of mode-locked lasers, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 105 (2022), pp. 044207-1--044207-6, DOI 10.1103/PhysRevE.105.044207 .
    Abstract
    Interaction equations governing slow time evolution of the coordinates and phases of two interacting temporal cavity solitons in a delay differential equation model of a nonlinear mirror mode-locked laser are derived and analyzed. It is shown that non-local pulse interaction due to gain depletion and recovery can lead either to a development of harmonic mode-locking regime, or to a formation of closely packed incoherent soliton bound state with weakly oscillating intersoliton time separation. Local interaction via electric field tails can result in an anti-phase or in-phase stationary or breathing harmonic mode-locking regime.

  • M. Wolfrum, S. Yanchuk, O. D'huys, Multiple self-locking in the Kuramoto--Sakaguchi system with delay, SIAM Journal on Applied Dynamical Systems, 21 (2022), pp. 1709--1725, DOI 10.1137/21M1458971 .
    Abstract
    We study the Kuramoto-Sakaguchi system of phase oscillators with a delayed mean-field coupling. By applying the theory of large delay to the corresponding Ott--Antonsen equation, we explain fully analytically the mechanisms for the appearance of multiple coexisting partially locked states. Closely above the onset of synchronization, these states emerge in the Eckhaus scenario: with increasing coupling, more and more partially locked states appear unstable from the incoherent state, and gain stability for larger coupling at a modulational stability boundary. The partially locked states with strongly detuned frequencies are shown to emerge subcritical and gain stability only after a fold and a series of Hopf bifurcations. We also discuss the role of the Sakaguchi phase lag parameter. For small delays, it determines, together with the delay time, the attraction or repulsion to the central frequency, which leads to supercritical or subcritical behavior, respectively. For large delay, the Sakaguchi parameter does not influence the global dynamical scenario.

  • M. Heida, M. Kantner, A. Stephan, Consistency and convergence for a family of finite volume discretizations of the Fokker--Planck operator, ESAIM: Mathematical Modelling and Numerical Analysis, 55 (2021), pp. 3017--3042, DOI 10.1051/m2an/2021078 .
    Abstract
    We introduce a family of various finite volume discretization schemes for the Fokker--Planck operator, which are characterized by different weight functions on the edges. This family particularly includes the well-established Scharfetter--Gummel discretization as well as the recently developed square-root approximation (SQRA) scheme. We motivate this family of discretizations both from the numerical and the modeling point of view and provide a uniform consistency and error analysis. Our main results state that the convergence order primarily depends on the quality of the mesh and in second place on the quality of the weights. We show by numerical experiments that for small gradients the choice of the optimal representative of the discretization family is highly non-trivial while for large gradients the Scharfetter--Gummel scheme stands out compared to the others.

  • L. Mertenskötter, K. Busch, R. DE J. León-Montiel, Entangled two-photon absorption spectroscopy with varying pump wavelength, Journal of the Optical Society of America. B, 38 (2021), pp. C63--C68, DOI 10.1364/JOSAB.428531 .
    Abstract
    In virtual-state spectroscopy, information about the energy-level structure of an arbitrary sample is retrieved by Fourier transforming sets of measured two-photon absorption probabilities of entangled photon pairs where the degree of entanglement and the delay time between the photons have been varied. This works well for simple systems but quickly becomes rather difficult when many intermediate states are involved. We propose and discuss an extension of entangled two-photon absorption spectroscopy that solves this problem by means of repeated measurements at different pump wavelengths. Specifically, we demonstrate that our extension works well for a variety of realistic experimental setups.

  • S. Slepneva, A. Pimenov, Nonlinear dynamical properties of frequency swept fiber-based semiconductor lasers, Journal of Physics: Photonics, 3 (2021), pp. 044002/1--044002/11, DOI 10.1088/2515-7647/ac1324 .
    Abstract
    We investigate dynamics of semiconductor lasers with fiber-based unidirectional ring cavity that can be used as frequency swept sources. We identify key factors behind the reach dynamical behaviour of such lasers using state-of-the-art experimental and analytical methods. Experimentally, we study the laser in static, quasi-static and synchronisation regimes.We apply experimental methods such as optical heterodyne or electric field reconstruction in order to characterise these regimes or study the mechanisms of transition between them. Using a delay differential equation model, we demonstrate that the presence of chromatic dispersion can lead to destabilisation of the laser modes through modulational instability, which results in undesirable chaotic emission. We characterise the instability threshold both theoretically and experimentally, and demonstrate deterioration of the FDML regime near the threshold.

  • I. Franović, O.E. Omel'chenko, M. Wolfrum, Bumps, chimera states, and Turing patterns in systems of coupled active rotators, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 104 (2021), pp. L052201/1--L052201/5, DOI 10.1103/PhysRevE.104.L052201 .
    Abstract
    Self-organized coherence-incoherence patterns, called chimera states, have first been reported in systems of Kuramoto oscillators. For coupled excitable units, similar patterns where coherent units are at rest, are called bump states. Here, we study bumps in an array of active rotators coupled by non-local attraction and global repulsion. We demonstrate how they can emerge in a supercritical scenario from completely coherent Turing patterns: a single incoherent unit appears in a homoclinic bifurcation, undergoing subsequent transitions to quasiperiodic and chaotic behavior, which eventually transforms into extensive chaos with many incoherent units. We present different types of transitions and explain the formation of coherence-incoherence patterns according to the classical paradigm of short-range activation and long-range inhibition.

  • V.V. Klinshov, S.Y. Kirillov, V.I. Nekorkin, M. Wolfrum, Noise-induced dynamical regimes in a system of globally coupled excitable units, Chaos. An Interdisciplinary Journal of Nonlinear Science, 31 (2021), pp. 083103/1--083103/11, DOI 10.1063/5.0056504 .
    Abstract
    We study the interplay of global attractive coupling and individual noise in a system of identical active rotators in the excitable regime. Performing a numerical bifurcation analysis of the nonlocal nonlinear Fokker-Planck equation for the thermodynamic limit, we identify a complex bifurcation scenario with regions of different dynamical regimes, including collective oscillations and coexistence of states with different levels of activity. In systems of finite size this leads to additional dynamical features, such as collective excitability of different types, noise-induced switching and bursting. Moreover, we show how characteristic quantities such as macroscopic and microscopic variability of inter spike intervals can depend in a non-monotonous way on the noise level.

  • M. Nizette, A.G. Vladimirov, Generalized Haus master equation model for mode-locked class-B lasers, Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, 104 (2021), pp. 014215/1--014215/13, DOI 10.1103/PhysRevE.104.014215 .
    Abstract
    Using the multiscale technique we develop a generalized version of the class-B Haus modelocking model that accounts for both the slow gain response to the averaged value of the field intensity and the fast gain dynamics on the scale comparable to the pulse duration. We show that unlike the standard class-B Haus mode-locked model, our model is able to describe not only Q-switched instability of the fundamental mode-locked regime, but also the appearance of harmonic mode-locked regimes with the increase of the pump power.

  • A. Zeghuzi, J.-P. Koester, M. Radziunas, H. Christopher, H. Wenzel, A. Knigge, Spatially modulated broad-area lasers for narrow lateral far-field divergence, Optics Express, 29 (2021), pp. 25133--25141, DOI 10.1364/OE.430804 .
    Abstract
    A novel laser design is presented that combines a longitudinal-lateral gain-loss modulation with an additional phase tailoring achieved by etching rectangular trenches. At 100 A pulsed operation, simulations predict a far-field profile with 0.3-degree full width at half maximum where a 0.4-degree-wide main lobe contains 40% of the emitted optical output power. While far-field measurements of these structured lasers emitting 10 ns long pulses with 35 W peak power confirm a substantial enhancement of radiation within the central one-degree angular range, the measured far-field intensity outside of the obtained central peak remains high.

  • H. Wenzel, M. Kantner, M. Radziunas, U. Bandelow, Semiconductor laser linewidth theory revisited, APPS. Applied Sciences, 11 (2021), pp. 6004/1--6004/29, DOI 10.3390/app11136004 .
    Abstract
    More and more applications require semiconductor lasers distinguished not only by large modulation bandwidths or high output powers, but also by small spectral linewidths. The theoretical understanding of the root causes limiting the linewidth is therefore of great practical relevance. In this paper, we derive a general expression for the calculation of the spectral linewidth step by step in a self-contained manner. We build on the linewidth theory developed in the 1980s and 1990s but look from a modern perspective, in the sense that we choose as our starting points the time-dependent coupled-wave equations for the forward and backward propagating fields and an expansion of the fields in terms of the stationary longitudinal modes of the open cavity. As a result, we obtain rather general expressions for the longitudinal excess factor of spontaneous emission (K-factor) and the effective Alpha-factor including the effects of nonlinear gain (gain compression) and refractive index (Kerr effect), gain dispersion and longitudinal spatial hole burning in multi-section cavity structures. The effect of linewidth narrowing due to feedback from an external cavity often described by the so-called chirp reduction factor is also automatically included. We propose a new analytical formula for the dependence of the spontaneous emission on the carrier density avoiding the use of the population inversion factor. The presented theoretical framework is applied to a numerical study of a two-section distributed Bragg reflector laser.

  • S. Amiranashvili, M. Radziunas, U. Bandelow, K. Busch, R. Čiegis, Additive splitting methods for parallel solutions of evolution problems, Journal of Computational Physics, 436 (2021), pp. 110320/1--110320/14, DOI 10.1016/j.jcp.2021.110320 .
    Abstract
    We demonstrate how a multiplicative splitting method of order Pcan be utilized to construct an additive splitting method of order P+3. The weight coefficients of the additive method depend only on P, which must be an odd number. Specifically we discuss a fourth-order additive method, which is yielded by the Lie-Trotter splitting. We provide error estimates, stability analysis of a test problem, and numerical examples with special discussion of the parallelization properties and applications to nonlinear optics.

  • A.G. Vladimirov, M. Tlidi, M. Taki, Dissipative soliton interaction in Kerr resonators with high-order dispersion, Physical Review A, 103 (2021), pp. 063505/1--063505/7, DOI 10.1103/PhysRevA.103.063505 .
    Abstract
    We consider an optical resonator containing a photonic crystal fiber and driven coherently by an injected beam. This device is described by a generalized Lugiato--Lefever equation with fourth order dispersion We use an asymptotic approach to derive interaction equations governing the slow time evolution of the coordinates of two interacting dissipative solitons. We show that Cherenkov radiation induced by positive fourth-order dispersion leads to a strong increase of the interaction force between the solitons. As a consequence, large number of equidistant soliton bound states in the phase space of the interaction equations can be stabilized. We show that the presence of even small spectral filtering not only dampens the Cherenkov radiation at the soliton tails and reduces the interaction strength, but can also affect the bound state stability.

  • A.G. Vladimirov, S. Suchkov, G. Huyet, S.K. Turitsyn, Delay-differential-equation model for mode-locked lasers based on nonlinear optical and amplifying loop mirrors, Physical Review A, 104 (2021), pp. 033525/1--033525/8, DOI 10.1103/PhysRevA.104.033525 .
    Abstract
    Delay differential equation model of a NOLM-NALM mode-locked laser is developed that takes into account finite relaxation rate of the gain medium and asymmetric beam splitting at the entrance of the nonlinear mirror loop. Asymptotic linear stability analysis of the continuous wave solutions performed in the limit of large delay indicates that in a class-B laser flip instability leading to a period doubling cascade and development of square-wave patterns can be suppressed by a short wavelength modulational instability. Numerically it is shown that the model can demonstrate large windows of regular fundamental and harmonic mode-locked regimes with single and multiple pulses per cavity round trip time separated by domains of irregular pulsing.

Beiträge zu Sammelwerken

  • A. Roche, U. Gowda, A. Kovalev, E. Viktorov, A. Pimenov, A.G. Vladimirov, M. Marconi, M. Giudici, G. Huyet, S. Slepneva, Defect mediated turbulence in a long laser, in: Real-time Measurements, Rogue Phenomena, and Single-Shot Applications VI, D.R. Solli, G. Herink, S. Bielawski, eds., 11671 of Proceedings of SPIE, SPIE. Digital Library, 2021, pp. 116710D/1--116710D/6, DOI 10.1117/12.2578727 .
    Abstract
    In this paper, we experimentally and theoretically analyse the formation and interaction of dark solitons in a long laser. The laser includes a semiconductor optical amplifier (SOA), centred around 1300nm, an intracavity filter and a fibre cavity whose length can vary from 20m to 20km. Near the lasing threshold the laser exhibits slowly evolving power dropouts the circulate the cavity. These dropouts are associated with the formation of Nozaki-Bekki Holes (NBH), also referred to as dark solitons. We observe both experimentally and numerically that the core of these holes exhibit chaotic dynamics and emit short light pulses. These pulses are found to be blue shifted with respect to the frequency of the dark solitons and therefore travel with a faster group velocity. These pulses are strongly damped, as they are detuned with respect to the filter transmission, but they may lead to the creation of new dark solitons. These pulses also play a major role in the development of optical turbulence when the filter is set at a frequency above 1310nm. In this case, the laser displays numerous dark solitons per round trip and the fast travelling pulses act as an interaction between the solitons, which can lead to the development of defect mediated turbulence.

  • A. Roche, U. Gowda, A. Kovalev, E. Viktorov, A. Pimenov, A.G. Vladimirov, M. Marconi, M. Giudici, G. Huyet, S. Slepneva, The formation of localised structures from the turn on transient of a long laser, in: Physics and Simulation of Optoelectronic Devices XXIX, B. Witzigmann, M. Osiński, Y. Arakawa, eds., 11680 of Proceedings of SPIE, SPIE Digital Library, 2021, pp. 116800N/1--116800N/6, DOI 10.1117/12.2578648 .

  • A. Zeghuzi, J.-P. Koester, M. Radziunas, H. Christopher, H. Wenzel, A. Knigge, Narrow lateral far field divergence obtained with spatially modulated broad-area lasers, in: 2021 27th International Semiconductor Laser Conference (ISLC), IEEE Xplore, IEEE, 2021, pp. 1--2, DOI 10.1109/ISLC51662.2021.9615888 .

Preprints, Reports, Technical Reports

  • A. Pimenov, A. Vladimirov, Temporal solitons in an optically injected Kerr cavity with two spectral filters, Preprint no. 2948, WIAS, Berlin, 2022, DOI 10.20347/WIAS.PREPRINT.2948 .
    Abstract, PDF (990 kByte)
    We investigate theoretically the dynamical behavior of an optically injected Kerr cavity where the chromatic dispersion is induced by propagation of light through two Lorentzian spectral filters with different widths and central frequencies. We show that this setup can be modeled by a second order delay differential equation that can be considered as a generalization of the Ikeda map with included spectral filtering, dispersion, and coherent injection terms. We demonstrate that this equation can exhibit modulational instability and bright localized structures formation in the anomalous dispersion regime.

  • S. Amiranashvili, Modeling of ultrashort optical pulses in nonlinear fibers, Preprint no. 2918, WIAS, Berlin, 2022, DOI 10.20347/WIAS.PREPRINT.2918 .
    Abstract, PDF (17 MByte)
    This work deals with theoretical aspects of pulse propagation. The core focus is on extreme, few-cycle pulses in optical fibers, pulses that are strongly affected by both dispersion and nonlinearity. Using Hamil- tonian methods, we discuss how the meaning of pulse envelope changes, as pulses become shorter and shorter, and why an envelope equation can still be used. We also discuss how the standard set of dispersion coefficients yields useful rational approximations for the chromatic dispersion in optical fibers. Three more specific problems are addressed thereafter. First, we present an alternative framework for ultra- short pulses in which non-envelope propagation models are used. The approach yields the limiting, shortest solitons and reveals their universal features. Second, we describe how one can manipulate an ultrashort pulse, i.e., to change its amplitude and duration in a predictable manner. Quantitative theory of the manipu- lation is presented based on perturbation theory for solitons and analogy between classical fiber optics and quantum mechanics. Last but not least, we consider a recently found alternative to the standard split-step approach for numerical solutions of the pulse propagation equations.

  • A. Grin, K.R. Schneider, Global algebraic Poincaré--Bendixson annulus for van der Pol systems, Preprint no. 2864, WIAS, Berlin, 2021, DOI 10.20347/WIAS.PREPRINT.2864 .
    Abstract, PDF (278 kByte)
    By means of planar polynomial systems topologically equivalent to the van der Pol system we demonstrate an approach to construct algebraic transversal ovals forming a parameter depending Poincaré-Bendixson annulus which contains a unique limit cycle for the full parameter domain. The inner boundary consists of the zero-level set of a special Dulac-Cherkas function which implies the uniqueness of the limit cycle. For the construction of the outer boundary we present a corresponding procedure

  • A.G. Vladimirov, M. Tlidi, M. Taki, Dissipative soliton interaction in Kerr resonators with high-order dispersion, Preprint no. 2843, WIAS, Berlin, 2021, DOI 10.20347/WIAS.PREPRINT.2843 .
    Abstract, PDF (1126 kByte)
    We consider an optical resonator containing a photonic crystal fiber and driven coherently by an injected beam. This device is described by a generalized Lugiato--Lefever equation with fourth order dispersion We use an asymptotic approach to derive interaction equations governing the slow time evolution of the coordinates of two interacting dissipative solitons. We show that Cherenkov radiation induced by positive fourth-order dispersion leads to a strong increase of the interaction force between the solitons. As a consequence, large number of equidistant soliton bound states in the phase space of the interaction equations can be stabilized. We show that the presence of even small spectral filtering not only dampens the Cherenkov radiation at the soliton tails and reduces the interaction strength, but can also affect the bound state stability.

  • L. Mertenskötter, K. Busch, R. DE J. León-Montiel, Entangled two-photon absorption spectroscopy with varying pump wavelength, Preprint no. 2837, WIAS, Berlin, 2021, DOI 10.20347/WIAS.PREPRINT.2837 .
    Abstract, PDF (647 kByte)
    In virtual-state spectroscopy, information about the energy-level structure of an arbitrary sample is retrieved by Fourier transforming sets of measured two-photon absorption probabilities of entangled photon pairs where the degree of entanglement and the delay time between the photons have been varied. This works well for simple systems but quickly becomes rather difficult when many intermediate states are involved. We propose and discuss an extension of entangled two-photon absorption spectroscopy that solves this problem by means of repeated measurements at different pump wavelengths. Specifically, we demonstrate that our extension works well for a variety of realistic experimental setups.

Vorträge, Poster

  • A. Pimenov, Localized structures in a passive ring cavity with two filters under optical injection, Nonlinear Waves and Turbulence in Photonics 2022, WIAS Berlin, July 15, 2022.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, French-German WE-Heraeus-Seminar : Outstanding Challenges in Nonlinear Dynamics, Les Houches, France, March 20 - 25, 2022.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, Leibniz MMS Days 2022, Potsdam, April 25 - 27, 2022.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, Dynamics Days Europe 2022, UK, August 22 - 26, 2022.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, Dynamics Days Europe 2022, August 22 - 26, 2022, University of Aberdeen, UK, August 22, 2022.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, Leibniz MMS Days 2022, April 25 - 27, 2022, WIAS, Potsdam, April 25, 2022.

  • A. Pimenov, Chromatic dispersion in delayed differential equations for optical cavities and localized structures, MURPHYS 2022- International Conference on Multiple Scale Systems and Hysteresis, May 30 - June 3, 2022, Mathematical Institute, Silesian University, Opava, Czech Republic, May 30, 2022.

  • S. Amiranashvili, Unusual ways of four-wave mixing instability, Nonlinear Waves and Turbulence in Photonics 2022, WIAS Berlin, July 14, 2022.

  • F. Severing, How numerics add to the instabilities of the generalised nonlinear Schrödinger equation, Nonlinear Waves and Turbulence in Photonics 2022, Berlin, July 14 - 15, 2022.

  • F. Severing , Nonlinear Schrödinger Equation - Flawless description of modulation instability?, Student Chapter Poster Session (SCPS) 2022 (Online Event), Sussex, UK, February 20, 2022.

  • S. Amiranashvili, Seminar zum Thema: Nicht Hermiteschen Operationen, August 10 - 11, 2022, TU Wien, Austria.

  • M. Radziunas, Modeling and simulation of semiconductor lasers for high emission power applications, 25th International Conference Mathematical Modelling and Analysis, May 30 - June 2, 2022, Vilnius Gediminas Technical University, Druskininkai, Lithuania, June 1, 2022.

  • M. Wolfrum, Bumps, chimera states, and Turing patterns in systems of coupled active rotators, French-German WE-Heraeus-Seminar: Outstanding Challenges in Nonlinear Dynamics, March 20 - 25, 2022, Wilhelm und Else Heraeus-Stiftung, Les Houches, France, March 23, 2022.

  • M. Wolfrum, Stability properties of temporal dissipative solitons in DDEs, Delay Days Utrecht 2022, Hasselt University, Utrecht, Netherlands, May 12, 2022.

  • M. Wolfrum, Synchronization transitions in systems of coupled phase oscillators, Leibniz MMS Days 2022, April 25 - 27, 2022, WIAS, Potsdam, April 26, 2022.

  • M. Stöhr, Bifurcations and instabilities of temporal dissipative solitons in DDE systems with large delay, Control of Self-Organizing Nonlinear Systems, Potsdam, August 29 - September 2, 2021.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators, Control of Self-Organizing Nonlinear Systems, Potsdam, August 29 - September 2, 2021.

  • L. Mertenskötter, M. Kantner, H. Wenzel , U. Bandelow, Modeling and optimization of semiconductor lasers for quantum metrology applications, MATH+ Day 2021 (Online Event), Technische Universität Berlin, November 5, 2021.

  • U. Bandelow, Modeling and simulation of the dynamics in semiconductor lasers (online talk), 91st Annual Meeting of the International Association of Applied Mathematics and Mechanics, MS1: ``Computational Photonics''' (Online Event), March 15 - 19, 2021, Universität Kassel, March 16, 2021.

  • U. Bandelow , Ultrashort solitons in the regime of event horizons in nonlinear dispersive optical media, Solvay Workshop on Dissipative Solitons and Optical Frequency Comb Generation, September 15 - 16, 2021, International Solvay Institutes, Brussels, Belgium, September 16, 2021.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators (online talk), Workshop on Control of Self-Organizing Nonlinear Systems, October 14 - 15, 2021, Technische Universität, Berlin, October 14, 2021.

  • A. Gerdes, Synchronization patterns in globally coupled Stuart--Landau oscillators (online talk), SFB Symposium ``Dynamical patterns in complex networks'' (Online Event), Technische Universität, Berlin, October 29, 2021.

  • M. Kantner, Mathematical modeling and optimal control of the COVID-19 pandemic (online talk), Mathematisches Kolloquium, Bergische Universität Wuppertal, April 27, 2021.

  • M. Kantner, Noise in semiconductor lasers (online talk), MATH+ Spotlight Seminar (Online Event), MATH+, July 14, 2021.

  • M. Radziunas, Cascaded polarization-coupling of high-power broad-area semiconductor lasers (online talk), European Semiconductor Laser Workshop (ESLW) 2021 (Online Event), September 17 - 18, 2021, Télécom Paris and Institut Polytechnique de Paris, France, September 17, 2021.

  • M. Radziunas, Modeling, simulation, and analysis of dynamics in semiconductor lasers (online talk), Research seminar of the Institute of Computer Science (Online Event), Vilnius University, Lithuania, September 29, 2021.

  • A.G. Vladimirov, Short pulse solutions of time-delay laser models (online talk), Dynamics Days Europe 2021 (Online Event), Minisymposium MS34 ``Time Delayed Systems: Theory and Experiments'', August 23 - 27, 2021, Université Côte d'Azur, Nice, France, August 27, 2021.

  • M. Wolfrum, Bumps, chimera states, and Turing patterns in systems of coupled active rotators, Control of Self-Organizing Nonlinear Systems, August 29 - September 2, 2021, Potsdam, September 2, 2021.

  • M. Wolfrum, Mode-locking and coherence echoes in systems of globally coupled phase oscillators (online talk), Nonlinear Dynamics of Oscillatory Systems (Online Event), September 19 - 22, 2021, Nizhny Novgorod, Russian Federation, September 21, 2021.

  • M. Wolfrum, Stability properties of temporal dissipative solitons in DDE systems (online talk), Dynamics Days Europe 2021 (Online Event), Minisymposium MS34: ``Time Delayed Systems: Theory and Experiment'', August 23 - 27, 2021, Université Côte d'Azur, Nice, France, August 27, 2021.

  • M. Wolfrum , Temporal dissipative solitons in systems of delay-differential equations (online talk), SIAM Conference on Applications of Dynamical Systems (Online Event), Minisymposium 184 ``Traveling Pulses in Delay and Lattice Differential Equations'', May 23 - 27, 2021, Portland, Oregon, USA, May 27, 2021.

Preprints im Fremdverlag

  • L. Schülen, A. Gerdes, M. Wolfrum, A. Zakharova, The solitary route to chimera states, Preprint no. 2204.00385, Cornell University Library, arXiv.org, 2022, DOI /10.48550/arXiv.2204.00385 .
    Abstract
    We show how solitary states in a system of globally coupled FitzHugh-Nagumo oscillators can lead to the emergence of chimera states. By a numerical bifurcation analysis of a suitable reduced system in the thermodynamic limit we demonstrate how solitary states, after emerging from the synchronous state, become chaotic in a period-doubling cascade. Subsequently, states with a single chaotic oscillator give rise to states with an increasing number of incoherent chaotic oscillators. In large systems, these chimera states show extensive chaos. We demonstrate the coexistence of many of such chaotic attractors with different Lyapunov dimensions, due to different numbers of incoherent oscillators.